Sensory Systems Flashcards
How are sensory stimuli received and processed by the body?
- sensory organs detect a physical or chemical stimulus in the environment
- specialized sensory cells detect these signals and code them as information to transmit and process thru the nervous system
What is sensory transduction?
the conversion of physical or chemical stimuli into nerve impulses
What are mechanoreceptors?
sensory receptors that respond to physical deformations of their membrane
touch, stretch, pressure, motion, sound
What are hair cells?
specialized mechanoreceptor that senses movement and mechanical vibrations
How do hair cells work?
- hair cells sense vibrations
- vibrations move stereocilia
- motion of stereocilia causes depolarization of the cell
- neurotransmitters are released
How do sound waves travel through the ear?
- sound waves travel into the outer ear
- travels thru ear canal and hits the eardrum, causing it to vibrate
- the vibration moves the ossicles, which transmit vibration to the oval window in the cochlea
What occurs in the basal membrane after the oval window is depressed by the ossicles?
- oval window creates waves that travel thru the cochlear fluid
- waves cause the basilar membrane to move
- movement of basilar membrane is transmitted into electrical impulses within the Organ of Corti
What happens to the hair cells when the basilar membrane moves?
- stereocilia on top of hair cells move against the tectorial membrane
- stereocilia bent toward the kinocilium stimulates the opening of K+ channels at the hair cell terminal, leading to depolarization
When the stereocilia are ____, the hair cell is at rest.
straight
When the stereocilia are bent ____ the kinocilium, the hair cell depolarizes, causing ____.
toward the kinocilium; stimulation
When the stereocilia are bent ____ the kinocilium, the hair cell hyperpolarizes, causing ____.
away from; inhibition
Hair cells at the base of the cochlea transmit ____ frequencies.
high
Hair cells at the apex of the cochlea transmit ____ frequencies.
low
What is the process of auditory transduction at the synapse of the hair cell and auditory nerve?
- K+ ions flow out of stereocilia and into hair cell, causing depolarization
- Depolarization stimulates the opening of Ca+ channels at the terminal
- Excitatory neurotransmitters are released into the synaptic cleft
- Neurotransmitters bind to ligand-gated ion channels of the afferent auditory nerve
- EPSPs are received by the afferent auditory nerve as graded potentials, which fire as action potentials to the brain when threshold is reached
- Signal is received by the brain and processed as sound
What are electromagnetic receptors?
Sensory cells that respond to electrical, magnetic, and light stimuli
What are photoreceptors?
light detecting electromagnetic receptors found in the eye
What protein converts light energy into electrical signals?
opsin
What light-absorbing pigment molecule is found in opsin?
retinal
What is the resting membrane potential of photoreceptor cells?
-35 mV
Why do photoreceptor cells have a more positive resting membrane potential than neurons?
leaky Na+ channels within the photoreceptor cells let in more Na+ ions at rest
What are cones?
photoreceptor cells in the retina responsible for color vision and greater spatial acuity
What are rods?
photoreceptor cells in the retina responsible for shades of grey and low light
What is glutamate?
an excitatory neurotransmitter that sends signals to the brain for visual processing
In the dark/light, photoreceptors release glutamate.
dark
In the dark/light, photoreceptors stop releasing glutamate.
light
Cis/trans retinal is bound to opsin in the dark.
cis
Cis/trans retinal is bound to opsin in the light.
trans
What happens in the photoreceptor cell in the dark?
- cis retinal is bound to opsin
- cGMP activates the opening of Na+ channels
- Na+ ions enter the cell, which causes depolarization
- glutamate neurotransmitters are released
What happens in the photoreceptor cell in the light?
- light strikes cis retinal, which changes it to trans retinal
- trans retinal dissociates from opsin
- opsin activates the G-protein transducin, which activates the effector phosphodiesterase
- the effector breaks down cGMP back to GMP
- lower cGMP concentration closes Na+ channels
- cell hyperpolarizes due to Na+ no longer entering the cell
- glutamate neurotransmitter release is inhibited
In what orde are cells involved in visual processing?
- cones/rods
- bipolar cells
- ganglion cells
In the light:
Cones/rods are ____, which ____ glutamate release onto the bipolar cell.
Bipolar cells are then ____, which ____ glutamate onto ganglion cells.
Ganglion cells are then ____, which allows it to ____.
hyperpolarized; decreases
depolarized; increases
depolarized; send signal to the brain
In the dark:
Cones/rods are ____, which ____ glutamate release onto the bipolar cell.
Bipolar cells are then ____, which ____ glutamate onto ganglion cells.
Ganglion cells are then ____, which ____.
depolarized; increases
hyperpolarized; reduces
hyperpolarized; prevents signal to the brain
You turn on a light so you can get a glass of water. At the moment the light turns ON, the relative amound of G⍺-GDP of trimeric G proteins ____.
decreases
when G⍺ is activated, GDP –> GTP
If the stereocilia of one hair cell becomes permanently bent away from the kinocilium, what would happen?
a single pitch will no longer be perceivable depending on the hair cell’s location
